A conventional float type drain trap is disclosed in Patent Literature 1, for example. This is such that an inlet port, a valve chamber, and an outlet are formed in a valve casing, a valve seat member is attached to the lower portion of the valve chamber, a discharge passage that communicates the valve chamber with the outlet side is formed to the valve seat member, a float that is moved away from and seated on the valve seat member to open and close the discharge passage is disposed in the valve chamber, an operation member whose tip end is disposed in the discharge passage is provided to be externally operable in the forward and backward directions, and a valve member that blocks the periphery anterior to and the periphery posterior to the middle portion of the operation member from one another when the operation member is in the most retracted position is provided in the middle portion of the operation member.